CPP water-wave capillary-wave daily-news 人生 python the-economist Leetcode hexo-stellar 诗词 cross product wedge product mathjax latex the-guardian Functional Analysis gravity-capillary-wave exterior algebra 春物 PINN Gamma Function Polygamma Fuction Zeta Function Bessel Function dyadic product Eulerian and Lagrangian Descriptions Gaussian Integral Hankel-Transform Bessel-Function capillary-gravity-wave Fourier-Transform Residue complex-analysis academic-Eng cpp-debug python-lambda